1. Field of the Invention
The present invention relates to an electric furnace and, more particular, relates to an electric furnace which holds easily and positively a heating member with small heat loss.
2. Description of the Related Art
Japanese Patent Application Laid-Open No. 183238/1995 discloses a supporting structure of a heating member for an electric furnace.
FIG. 12 shows a perspective view of a portion of the conventional electric furnace a portion of which being cut away.
FIG. 13 shows a perspective view of a portion of the electric furnace shown in FIG. 12.
A reference numeral 1 denotes a heat insulating cylindrical furnace wall, 2 denotes a heater of an electric resistance wire wound helically along an inner peripheral surface of the heat insulating cylindrical furnace wall 1, 3 denotes a plurality of wire supporting member fixed on the inner peripheral surface of the furnace wall so as to separate with a predetermined space to one another in the circumference direction of the furnace wall, 4 denotes a hole formed in the wire supporting member 3, through which the electric resistance wire is passed. The wire supporting member 3 has a trapezoidal cross section tapering to one side facing the center of the furnace.
In the conventional electric furnace mentioned-above, a contact area of the heat wire 2 passing through the hole 4 with respect to the wire supporting member 3 becomes smaller than that in case of a wire supporting member having a rectangular cross section, so that an area of exposed portion of the heat wire 2 and a generating heat quantity become larger therefore, and that it is possible to reduce the heat radiation loss due to the wire supporting member 3.
However, in the electric furnace mentioned-above the reduction of the heat radiation loss is still insufficient.